Electrode and connecting designs for roll-to-roll format flexible display manufacturing

ABSTRACT

The present invention generally is directed to electrode designs suitable for roll-to-roll format flexible manufacturing of an EPD.  
     It is also directed to an EPD having a segment design in a repeated pattern across an entire roll of the display. The EPD preferably is microcup-based. The EPD manufactured according to the present invention has the appearance of a roll of wall paper and it can be cut into any desired sizes or formats. The EPD has electrode or trace lines which may be exposed by asymmetrical cutting and stripping without the need of precision registration.

RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. ProvisionalApplication No. 60/385,053 filed May 29, 2002, which is incorporatedherein by reference in its entirety.

BACKGROUND OF THE INVENTION

[0002] An electrophoretic display (EPD) is a non-emissive device basedon the electrophoresis phenomenon influencing charged pigment particlessuspended in a colored dielectric solvent. This type of display wasfirst proposed in 1969. An EPD typically comprises a pair of opposed,spaced-apart plate-like electrodes, with spacers predetermining acertain distance between the electrodes. At least one of the electrodes,typically on the viewing side, is transparent.

[0003] When a voltage difference is imposed between the two electrodes,the pigment particles migrate by attraction to the plate of polarityopposite that of the pigment particles. Thus, the color showing at thetransparent plate, determined by selectively charging the plates, can beeither the color of the solvent or the color of the pigment particles.Reversal of plate polarity will cause the particles to migrate back tothe opposite plate, thereby reversing the color. Intermediate colordensity (or shades of gray) due to intermediate pigment density at thetransparent plate may be obtained by controlling the plate chargethrough a range of voltages or pulsing time.

[0004] EPDs of different pixel or cell structures have been reportedpreviously, for example, the partition-type EPD (M. A. Hopper and V.Novotny, IEEE Trans. Electr. Dev., Vol. ED 26, No. 8, pp. 1148-1152(1979)) and the microencapsulated EPD (U.S. Pat. Nos. 5,961,804 and5,930,026).

[0005] An improved EPD technology was recently disclosed in co-pendingapplications, U.S. Ser. No. 09/518,488, filed on Mar. 3, 2000(corresponding to WO 01/67170 published on Sep. 13, 2001), U.S. Ser. No.09/606,654, filed on Jun. 28, 2000 (corresponding to WO 02/01281published on Jan. 3, 2002) and U.S. Ser. No. 09/784,972, filed on Feb.15, 2001 (corresponding to WO02/65215 published on Aug. 22, 2002), allof which are incorporated herein by reference. The improved EPDcomprises isolated cells formed from microcups of well-defined shape,size and aspect ratio and filled with an electrophoretic fluidcomprising charged particles dispersed in a dielectric solvent. Thefilled cells are individually sealed with a polymeric sealing layer,preferably formed from a composition comprising a material selected froma group consisting of thermoplastics, thermosets and precursors thereof.

[0006] The microcup wall in fact is a built-in spacer or support to keepthe top and bottom substrates apart at a fixed distance and providessuperior mechanical properties and structural integrity. Since thedisplay fluid within the display prepared by the microcup technology isenclosed and isolated in each cell, the microcup-based display may becut into almost any dimensions without the risk of damaging the displayperformance due to the loss of display fluid in the active areas.

[0007] The microcup structure also enables a format flexible andefficient roll-to-roll continuous manufacturing process for EPDs,particularly for thin, flexible and durable EPDs. The displays can beprepared on a continuous web of a conductor film such as ITO/PET by, forexample, (1) coating a radiation curable composition onto a conductorfilm (i.e., ITO/PET film), (2) forming the microcup structure by amicroembossing or photolithographic method, (3) filling the microcupswith an electrophoretic fluid and sealing the filled microcups, (4)laminating the sealed microcups with a second conductor film and (5)slicing and cutting the display into a desirable size or format forassembling. To complete the construction of a display device, theelectrode lines of the display must be exposed and connected to a drivercircuitry.

[0008] However, not all electrode designs are suitable for use in aroll-to-roll format flexible manufacturing process. In fact,implementation of the roll-to-roll process is severely limited by thedesign of the electrodes (and, if present, also the via holes and tracelines) connecting to a driver circuitry. To enable a roll-to-roll formatflexible process, the electrodes and connecting traces require specialdesigns. However, the pitch sizes of the electrode lines of thespecially designed electrodes very often are not compatible with thoseof the commonly used drivers. Consequently, an expensive fan-in/fan-outflexible circuitry is typically needed as an adapter to bridge theelectrode lines and the driver circuit. Bonding the fan-in/fan-outflexible circuitry to both the display panel and the driver is anexpensive and time-consuming process.

[0009] Accordingly, in order to reduce the cost of manufacturing andmaintaining display modules which typically comprise a display panel,driver and necessary circuitries, there is a strong need for a systemwhich is more reliable, easier to install and maintain and suitable forroll-to-roll format flexible manufacturing.

SUMMARY OF THE INVENTION

[0010] The present invention is directed to electrode designs suitablefor roll-to-roll format flexible manufacturing of an EPD.

[0011] The invention is also directed to an EPD having a segment designin a repeated pattern across an entire roll of the display. The EPDpreferably is microcup-based. The EPD manufactured according to thepresent invention has the appearance of a roll of wall paper and it canbe cut into any desired sizes or formats. The EPD has electrodes ortrace lines which may be exposed by asymmetrical cutting and strippingwithout the need of precision registration.

[0012] More specifically, the first aspect of the invention is directedto an electrode design suitable for roll-to-roll format flexiblemanufacturing of passive matrix EPDs. The electrode design comprisescontinuous row electrodes having substantially the same width (W-1) andsubstantially the same line gap (G-1) across the entire roll andcontinuous column electrode lines having substantially the same width(W-2) and substantially the same line gap (G-2) across the entire roll.The width W-1 may be the same as or different from the width W-2.Similarly the line gap G-1 may be the same as or different from the linegap G-2.

[0013] The second aspect of the present invention is directed to anelectrode design wherein the row and column electrodes form an obliqueangle from the direction of a support web. More specifically, the rowelectrodes may have an angle of from about 35° to about 55°, preferably45°, from the direction of the web and the column electrodes form anangle of about 90° from the row electrodes.

[0014] The third aspect of the present invention is directed to anelectrode design including, if present, the via holes and connectingtraces, for a segment EPD having a segment design in a repeated patternof the same size, shape, orientation and spacing between adjacentsegments. Such segment EPDs may be used for digital clocks, e-signs ande-price tags.

[0015] The fourth aspect of the present invention is directed to a novelconnecting system for a display module. The system does not needprecision bonding of the display panel to a driver circuitry and is morereliable and easier to install and maintain.

[0016] The fifth aspect of the present invention is directed to a novelEPD system, especially suitable for use as price tags. In this system,an EPD panel is inserted or snapped into an open slot of a basestructure which is connected to driver and controller circuits. Noassembling or complicated bonding of the EPD panel to the base structureis needed. The contact pads in the base structure are prearranged tocorrespond precisely to the electrode contacts of the EPD panel. Nofan-in/fan-out flexible adapter that connects the panel to the drivercircuitry is required.

[0017] The sixth aspect of the present invention is directed to analternative system, also suitable for use as price tags. In this system,an EPD panel is inserted into a base structure from the front open faceof the structure and then secured by a front plate. Alternatively, thedriver circuit may be integrated into the EPD panel. A furtheralternative is that both the driver and controller circuitries areintegrated in the EPD panel.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 depicts a typical display cell prepared by the microcuptechnology.

[0019] FIGS. 2A-2C illustrate one of the electrode designs of thepresent invention.

[0020] FIGS. 3A-3C illustrate an alternative electrode design of thepresent invention wherein the row electrodes have an oblique angle froma support web.

[0021] FIGS. 4A-4G illustrate segment electrode designs of the presentinvention.

[0022]FIG. 5 illustrates the connecting design of the present invention.

[0023] FIGS. 6-9 illustrate the price tag systems of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

[0024] Technical Background

[0025] Preparation of Micro-Cup Based Display Panel

[0026]FIG. 1 depicts a typical display cell prepared by the microcuptechnology as disclosed in WO01/67170. The microcup-based display cell(10) is sandwiched between a first electrode layer (11) and a secondelectrode layer (12). A primer layer (13) is optionally present betweenthe cell and the second electrode layer (12). The cell (10) is filledwith an electrophoretic fluid and sealed with a sealing layer (14). Thefirst electrode layer (11) is laminated onto the sealed cell optionallywith an adhesive (15).

[0027] The display panel may be prepared by microembossing orphotolithography as disclosed in WO01/67170. In the microembossingprocess, an embossable composition is coated onto the conductor side ofthe second electrode layer (12) and embossed with a male mold to producearrays of microcups. To improve the mold release property, the conductorlayer may be pretreated with a thin primer layer (13) before coating theembossable composition.

[0028] The embossable composition may comprise a thermoplastic,thermoset or precursor thereof which may be a multifunctional acrylateor methacrylate, vinylbezene, vinylether, epoxide, an oligomer orpolymer thereof, or the like. Multifunctional acrylate and its oligomersare the most preferred. A combination of a multifunctional epoxide and amultifunctional acrylate is also useful to achieve desirablephysico-mechanical properties. A crosslinkable oligomer impartingflexibility, such as urethane acrylate or polyester acrylate, is usuallyalso added to improve the flexure resistance of the embossed microcups.The composition may contain an oligomer, a monomer, additives andoptionally a polymer. The glass transition temperature (Tg) for theembossable composition usually ranges from about −70° C. to about 150°C., preferably from about −20° C. to about 50° C.

[0029] The microembossing process is typically carried out at atemperature higher than the Tg. A heated male mold or a heated housingsubstrate against which the mold presses may be used to control themicroembossing temperature and pressure.

[0030] The mold is released during or after the precursor layer ishardened to reveal the microcups (10). The hardening of the precursorlayer may be accomplished by cooling, solvent evaporation, cross-linkingby radiation, heat or moisture. If the curing of the thermoplastic orthermoset precursor is accomplished by UV radiation, UV may radiate ontothe thermoplastic or thermoset precursor layer through the transparentconductor layer. Alternatively, UV lamps may be placed inside the mold.In this case, the mold must be transparent to allow the UV light toradiate on to the thermoplastic or thermoset precursor layer.

[0031] The microcups are then filled with an electrophoretic fluid andsealed as disclosed in co-pending applications, U.S. Ser. No.09/518,488, filed on Mar. 3, 2000 (corresponding to WO 01/67170), U.S.Ser. No. 09/606,654, filed on Jun. 28, 2000 (corresponding to WO02/01281) and U.S. Ser. No. 09/784,972, filed on Feb. 15, 2001(corresponding to WO02/65215), all of which are incorporated herein byreference.

[0032] The sealing of the microcups may be accomplished in a number ofways. Preferably, it is accomplished by overcoating the filled microcupswith a sealing composition comprising a solvent and a rubber materialselected from the group consisting of thermoplastic elastomers,polyvalent acrylate or methacrylate, cyanoacrylates, polyvalent vinylincluding vinylbenzene, vinylsilane, vinylether, polyvalent epoxide,polyvalent isocyanate, polyvalent allyl, oligomers or polymerscontaining crosslinkable functional groups, and the like. Additives suchas a polymeric binder or thickener, photoinitiator, catalyst, filler,colorant or surfactant may be added to the sealing composition toimprove the physico-mechanical properties and the optical properties ofthe display. The sealing composition is incompatible with theelectrophoretic fluid and has a specific gravity no greater than that ofthe electrophoretic fluid. Upon solvent evaporation, the sealingcomposition forms a conforming seamless seal on top of the filledmicrocups. The sealing layer may be further hardened by heat, radiationor other curing methods. Sealing with a composition comprising athermoplastic elastomer is particularly preferred. Examples ofthermoplastic elastomers may include, but are not limited to, tri-blockor di-block copolymers of styrene and isoprene, butadiene orethylene/butylene, such as the Kraton™ D and G series from KratonPolymer Company. Crystalline rubbers such aspoly(ethylene-co-propylene-co-5-methylene-2-norbornene) and other EPDM(Ethylene Propylene Diene Rubber terpolymer) from Exxon Mobil have alsobeen found useful.

[0033] Alternatively, the sealing composition may be dispersed into anelectrophoretic fluid and filled into the microcups. The sealingcomposition is incompatible with the electrophoretic fluid and islighter than the electrophoretic fluid. Upon phase separation andsolvent evaporation, the sealing composition floats to the top of thefilled microcups and forms a seamless sealing layer thereon. The sealinglayer may be further hardened by heat, radiation or other curingmethods. The sealed microcups finally are laminated with the firstelectrode layer (11) optionally pre-coated with an adhesive layer (15).

[0034] The entire process as described above may be carried outroll-to-roll continuously as disclosed in a co-pending application, U.S.Ser. No. 09/784,972 filed on Feb. 15, 2001, the content of which isherein incorporated by reference. Briefly, the microcup-based displaycells are formed integrally with one another as portions of a structuredtwo-dimensional array assembly on a moving web. The web upon which themicrocups are formed includes a display addressing array comprising apreformed electrode layer, such as one with ITO conductor lines. Theelectrode layer (ITO lines) is coated with the embossable composition asdescribed above for formation of the microcups.

[0035] In practice, the preformed electrode layer (corresponding to 12in FIG. 1) on the web is transparent which ultimately may be the viewingside of the display.

[0036] The Cutting/Stripping Process

[0037] To expose the electrode for circuitry connection, a strip coatingor patch coating process may be employed to deposit the embossablecomposition (for forming the microcups) onto selected areas of thesubstrate. However, this process has many disadvantages. An improvedprocess of exposing the electrode lines was disclosed in a co-pendingapplication, U.S. Ser. No. 10/422,608 filed on Apr. 23, 2003, which isincorporated herein by reference. The improved process involves (1)cutting the EPD panel to a desired dimension and shape, followed byremoving one electrode layer (for example 11, in FIG. 1) in apredetermined area by, for example, a die, diamond, knife or a lasercutting method to expose the layers underneath (which may include theadhesive layer, sealing layer, microcups layer and primer layer), (2)stripping off the exposed layers by, for example, a stripping, solventor solution and finally (3) connecting the exposed conductor lines onthe other electrode layer (12 in FIG. 1) to a driver circuitry. Thisprocess may be repeated to expose the electrode lines or patterns of theEPD panel in other areas, when required, for connection to a drivercircuitry.

[0038] To improve the strippability of the exposed layers in step (2)above, a polymeric additive that is soluble or dispersible in an organicor aqueous stripper may be added to the embossing composition forforming the microcups. If an aqueous stripper is used, suitablepolymeric additives for the embossing composition may include, but arenot limited to, water soluble or dispersible polymers such aspolyethylene glycol, poly(2-ethyl-2-oxazoline), polyvinylpyrrolidone(PVP), hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC) andcopolymers or block copolymers thereof, acidic or basic copolymersderived from acrylic acid or methacrylic acid such as Carboset 515 (fromBFGoodrich, Cleveland, Ohio), itaconic acid, maleic anhydride, vinylphthalate and vinylpyridine. If an organic stripper is used, suitablepolymeric additives for the embossing composition may include, but arenot limited to, solvent soluble or dispersible polymers or oligomerssuch as polyester, polyvinyl butyral, acrylic or methacrylic copolymers,styrene copolymers, polycaprolatones, polyethers, polycarbonates,polyamides and polyurethanes.

[0039] The composition of the primer layer may be the same or differentfrom the embossing composition. The sealing composition may be one ofthe sealing compositions described above.

[0040] Preferred materials for the strippable adhesive layer may beformed from an adhesive or a mixture thereof selected from a groupconsisting of pressure sensitive, hot melt and radiation curableadhesives. The adhesive materials may include, but are not limited to,acrylics, styrene-butadiene copolymers, styrene-butadiene-styrene blockcopolymers, styrene-isoprene-styrene block copolymers, polyvinylbutyal,cellulose acetate butyrate, polyvinylpyrrolidone, polyurethanes,polyamides, ethylene-vinylacetate copolymers, epoxides, multifunctionalacrylates, vinyls, vinylethers, and their oligomers, polymers andcopolymers. Adhesives comprising polymers or oligomers having a highacid or base content such as polymers or copolymers formed from acrylicacid, methacrylic acid, itaconic acid, maleic anhydride, vinylpyridineand derivatives thereof are particularly useful for an aqueous strippingprocess. The adhesive layer may be post cured by, for example, heat orradiation such as UV after lamination.

[0041] When a display panel is subjected to cutting and stripping toexpose the conductor lines or patterns for connection to a drivercircuitry, one of the electrode layers, for example, the first electrodelayer (11) in FIG. 1, in a predetermined area, usually at the end of thepanel, is first removed by, for example, a die, diamond, knife or alaser cutting method. The cut may optionally extend into the layersunderneath (e.g., the adhesive layer, sealing layer, microcup layer andprimer layer), but not into the second electrode layer (12). Beforestripping, preferably an edge seal material is applied to the edge linesbetween all layers not to be stripped, on all sides. The edge sealmaterial protects the layers not to be stripped from the strippingsolvent or solution used during stripping. The adhesive, sealing,microcup and primer layers are then stripped off using a strippingsolvent, such as benzyl alcohol, isopropyl acetate, butyl acetate,methoxyethanol, butanol, toluene, xylene, cyclohexanone or ketones,lactones, esters, ethers, alcohols, amides, pyrrolidones or derivativesor mixtures thereof. Alternatively, the layers may be stripped off usingan aqueous stripper, such as aqueous developer Shipley 453 or CD26 (fromShipley, Marlborough, Mass.), which is particularly useful if an acidcomposition is used for the adhesive, sealing, microcup or primer layer.Stripping may also be assisted by spraying of the stripper with a nozzleor compressed air or application by a soft brush and other mechanical orphysical means.

[0042] The cutting/stripping process as described above removes thelayers in the area except the second electrode layer (12). As a result,the second electrode layer in the area is exposed and the conductorlines on the exposed area may then be connected to a driver circuitry.The same stripping process may similarly be carried out to expose theconductor lines on the first electrode layer (11) in a different areafor connection to a driver circuit.

[0043] I. Electrode Designs of the Present Invention

[0044] In one of the electrode designs is shown in FIG. 2A, themicrocup-based cells (not shown) are sandwiched between a top rowelectrode layer (21) and a bottom column electrode layer (22).

[0045] In a roll to roll continuous process, the top row electrode layerand the bottom column electrode layer are on two separate moving webs.The top row electrode layer (21) has row electrodes aligned with the webmoving direction (see arrow). The column electrodes on another movingweb are perpendicular to the row electrodes. The moving row electrodeweb and the moving column electrode web are finally aligned forconstruction of a display panel.

[0046] All the row electrodes have substantially the same electrodewidth (21 a) and substantially the same electrode gap (21 b). All thecolumn electrodes have substantially the same electrode width (22 a) andsubstantially the same electrode gap (22 b). The width of the rowelectrodes (21 a) may be the same as the width of the column electrodes(22 a). The gap between the row electrodes (21 b) may also be the sameas the gap between the column electrodes (22 b). The width of theelectrodes generally may be in the range of about 20 to about 5000microns, preferably about 100 to about 1000 microns. The gap between theelectrodes may be in the range of about 5 to about 500 microns,preferably about 5 to about 100 microns.

[0047] One approach to fabricate such a patterned electrode layertypically involves the use of photolithographic techniques and chemicaletching. Conductor films useful for plastic display applications may beformed by a process such as laminating, electroplating, sputtering,vacuum deposition or a combination thereof, for forming a conductor filmonto a plastic substrate. Useful thin film conductors include metalconductors such as aluminum, copper, zinc, tin, molybdenum, nickel,chromium, silver, gold, iron, indium, thallium, titanium, tantalum,tungsten, rhodium, palladium, platinum or cobalt, and the like, andmetal oxide conductors such as indium tin oxide (ITO) or indium zincoxide (IZO), as well as alloys or multilayer composite films derivedfrom the aforementioned metals and/or metal oxides. Further, the thinfilm structures described herein may comprise either a single layer thinfilm or a multilayer thin film. ITO films are of particularly interestin many applications because of their high degree of transmission in thevisible light region. Useful plastic substrates include epoxy resins,polyimide, polysulfone, polyarylether, polycarbonate (PC), polyethyleneterephthalate (PET), polyethylene terenaphthalate (PEN), poly(cyclicolefin) and composites thereof. The conductor-on-plastics films aretypically patterned by a photolithographic process which comprises stepsincluding (1) coating the conductor film with photoresist; (2)patterning the photoresist by image-wise exposing it through a photomaskto, for example, ultraviolet light; (3) “developing” the patterned imageby removing the photoresist from either the exposed or the unexposedareas, depending on the type of photoresist used, to uncover theconductor film in areas from which it is to be removed (i.e., areaswhere no electrode lines is to be located); (4) using a chemical etchingprocess to remove the conductor film from the areas from which thephotoresist has been removed; and (5) stripping the remainingphotoresist to uncover the electrode lines.

[0048] The electrode design of FIG. 2A can be easily connected to adriver circuit without a fan-in/fan-out adaptor. It is particularlysuitable for the connecting system of the present invention (see SectionIII below). The display panel may be cut into any desired shapes andsizes.

[0049] The dotted lines (26) in FIG. 2A indicates the cutting of thepanel into three small panels (23, 24 and 25)

[0050]FIG. 2B illustrates how the conductor lines on panel 23 may beexposed and connected to a driver circuit. The panel is subjected to thecutting/stripping process as described above to expose the conductorlines on the electrode layers in predetermined areas (27 and 28) forconnection to a driver circuitry. FIG. 2C shows a 3-dimensional view ofthis configuration. This electrode design enables the display panel tobe fabricated in a roll-to-roll process with format flexibility.

[0051] An alternative electrode design suitable for roll-to-roll formatflexible manufacturing of a passive matrix EPDs is shown in FIG. 3A. Themicrocup-based cells (not shown) are sandwiched between a top rowelectrode layer (31) and a bottom column electrode layer (32).

[0052] The row and column electrodes form an oblique angle from thedirection of a support web (see arrow). More specifically, the rowelectrodes are arranged in an angle of from about 35° to about 55°,preferably 45°, from the moving direction of the web. The columnelectrodes of the bottom column electrode layer (32) may form an angleof about 90-degree from the row electrodes.

[0053] All the row electrodes have substantially the same electrodewidth (31 a) and substantially the same electrode gap (31 b). All thecolumn electrodes have substantially the same electrode width (32 a) andsubstantially the same electrode gap (32 b). The width of the rowelectrodes (31 a) may be the same as the width of the column electrodes(32 a). The gap between the row electrodes (31 b) may be the same as thegap between the column electrodes (32 b). The width of the electrodesmay be in the range of about 20 to about 5000 microns, preferably about100 to about 1000 microns. The gap between the electrodes may be in therange of about 5 to about 500 microns, preferably about 5 to about 100microns.

[0054] This type of electrode layer may be fabricated in the same manneras described above for the electrode design of FIG. 2A.

[0055] Electrode lines forming an oblique angle, especially a 45-degreeangle, with the web direction is particularly suitable for aroll-to-roll manufacturing process. They are easier to be fabricatedthan the electrode lines aligned in the web direction (0 degree). Firstof all, electrode lines at an oblique angle from the moving directionare shorter in length than electrode lines aligned in the web direction.In addition, electrode lines aligned in the web direction are difficultto manufacture and easy to break during the roll-to-roll process.Furthermore, the on-line inspection for the electrode continuity of theelectrode lines aligned with the web direction is also difficult.

[0056] The electrode design of FIG. 3A can also be easily connected to adriver circuit without a fan-in/fan-out adaptor. An EPD panel having theelectrode design of FIG. 3A can be cut into any desired sizes andshapes. The dotted lines (36) show the cutting of a panel (33) out of alarge panel (FIG. 3B).

[0057]FIG. 3C illustrates how the conductor lines on panel 33 may beexposed and connected to a driver circuit, following the cutting andstripping steps as described above.

[0058] II. Segment Display Panel of the Present Invention

[0059] The segment electrode design as shown in FIG. 4A is suitable forroll-to-roll format flexible manufacturing of a segment EPD. Themicrocup-based cells (not shown) are formed by embossing on atransparent common electrode layer (not shown) which ultimately may bethe viewing side of the display. The embossing is carried out on theentire panel. The microcups formed are then filled with anelectrophoretic dispersion and sealed as previously described. A segmentelectrode layer is then laminated over the sealed microcups to completethe EPD panel. The segment electrodes may be formed on a substrate (41).Suitable substrate materials may include, but are not limited to, PET[poly(ethylene terephthalate)], PEN (polyethylene naphthalate), PC(polycarbonate), polysulphone, polyimide, polyarylether, epoxy, phenolicand composites thereof. The traces (48) may be formed on the same sideof the segment electrodes (42) or on the opposite side when vias(through holes) are present. The segment electrodes (42) are arranged ina repeating pattern along the web moving direction (see arrow).

[0060] The common electrode layer is a single piece which covers theentire display area.

[0061] The segment electrode pattern is symmetrical in one or moredirections or axes and is also substantially seamless. In other words,the display panel may have a wallpaper type of design and the panel maybe cut into any desired formats, shapes or sizes, depending onapplications as illustrated in FIGS. 4B-4F.

[0062]FIG. 4B shows a display panel having both a repeated pattern of a14-segment alphanumerical design (the top line) and a repeated patternof a 7-segment design (the bottom line). FIG. 4C demonstrates cutting asmall panel out of the original panel and the cutout panel has only the7-segment pattern. FIG. 4D demonstrates cutting a small panel out of theoriginal panel and the cutout panel has only the 14-segment pattern.FIG. 4E demonstrates cutting the original panel into two pieces, eachhaving a combination of the 7-segment pattern and the 14-segmentpattern. FIG. 4F demonstrates that the cut-out panels may be stitchedtogether to form a new panel having a combination of the 7-segmentpattern and the 14-segment pattern.

[0063] The segment display has a variety of applications. For example,it may be used as a digital clock display (e.g., 05:30), a calendardisplay (e.g., Dec. 25, 2002 or Dec. 25, 2002) or a price tag display(e.g., 230.40). The three dots between the segment patterns may beturned on or off, depending on the applications.

[0064]FIG. 4G shows a 4 digit panel (43) cut out of the panel of FIG. 4Aalong the dotted lines (46). The cut-out panel is subjected to thecutting and stripping steps as described above to expose the electrodelines for connection to a driver circuit. The resulting panel is thenused in the connecting system as described below.

[0065] III. Connecting System of the Present Invention

[0066] The connecting system of a flat panel display typically involveseither precision bonding or complicated mechanical devices, which arecostly and difficult to maintain. These shortcomings are eliminated inthe connecting system of the present invention which may be applied toeither a passive matrix display panel or a segment display panel.

[0067] 1. Passive Matrix Display Panel

[0068] The novel connecting system is illustrated in FIG. 5.

[0069]FIG. 5 shows a novel connecting system for passive matrix displaymodule. The row electrodes (51) and the column electrodes (52) of thepassive matrix panel (53) are routed to the edge of a panel. In thisembodiment, the electrode design of the panel is that of FIG. 2A. Inaddition, the row electrodes are facing the non-viewing side of thepanel and the column electrodes are facing the viewing side of thepanel. However, when vias (conducting through holes) are used, the rowand column electrodes may face the same direction. A base structure (54)comprises driving and controller circuitries and the connecting system.The passive matrix display panel is insertible into the base structure.The connection system usually comprises contact pads (55 b) in the basestructure that match the electrode contacts (55 a) on the row and columnelectrodes of the display panel. When a display panel is inserted intothe base structure, the electrode contacts (55 a) of the row and columnelectrodes become in contact with the driver circuit through the contactpads (55 b) in the base structure. The contact between the electrodecontacts and the contact pads can be a tight-fit design, which requiresa higher insertion force but provides more reliable contact.Zero-insertion force design can also be used with a mechanical clampingdevice to secure the display panel to ensure contact.

[0070] Alternatively, a connecting system may be similarly constructedfor the electrode design of FIG. 3A.

[0071] 2. Segment Display Panel

[0072] The connecting system may also be used for a segment displaypanel. In this assembly, the segment display panel is also insertibleinto the base structure. The segment electrodes have electrode contactswhich may be in contact with the contact pads in a base structure tocause driving of the display panel by a driver circuit.

[0073] IV. Price Tag System of the Present Invention

[0074] Price tags and sales sign are an essential operation feature insupermarkets and stores. Because the prices of the merchandise changefrom time to time, the price tags need to be updated regularly. Printingnew tags and placing them at the proper locations is a verylabor-intensive and costly process. In fact, it is one of the majoroperation costs for most stores.

[0075] Electronic price tags have been known for many years. LCD and LEDhave been proposed for use in such applications. However, both types ofdisplay are bulky and very power demanding, and therefore are difficultto be integrated into the shelf structures in the stores. They alsorequire a complicated wiring system to connect the panel to the driverand controller circuitries. LCD and LED are also fragile and difficultto maintain.

[0076] FIGS. 6-9 illustrate a novel price tag system.

[0077] In FIG. 6, an electrophoretic display panel (60) is laminatedonto a supporting substrate (not shown). Suitable supporting substratesmay include, but are not limited to, acrylics, polystyrene,polycarbonate, polyimide, polyester, polysulfone, polyamides,polyurethane, epoxy, phenolic, melamine and copolymers, blends orcomposites thereof. Polycarbonate, polyester, polyimide, polysulfone,phenolic resins and composites or blends thereof are the most preferred.

[0078] The figure shows the display panel partially inserted into a basestructure (61) through an open slot (62). The base structure is areceptacle for the display panel and has a front panel (63) and a backpanel (64). The segment electrodes (65) have electrode contacts (66 a).For illustration purpose, the electrode contacts (66 a) can be seen inthe figure. However, it should be noted that in this embodiment, theelectrode contacts (66 a) may be located on the non-viewing side or theviewing side of the segment electrodes.

[0079] A circuit board (67) may be built into the base structure. On thecircuit board (67), the display driver, controller and communicationcircuits (none of them shown) are on one side or both sides of theboard, whereas contact pads (66 b) are on only one side of the board. Inone embodiment, the contact pads (66 b) are on the side of the circuitboard facing the non-viewing side of the display panel to allow thecontact pads (66 b) to be in contact with the electrode contacts (66 a).

[0080] After the display panel is fully inserted into the base structureand firmly secured in its position within the base structure, theelectrode contacts (66 a) behind the segment electrodes are in contactwith the contact pads (66 b) on the circuit board. The contact providesconnection between the display panel and the circuit board. The drivercircuit and other components on the circuit board then drive the displaypanel.

[0081] In this design, preferably there is a side-locking panel (68),which may be pressed into the base structure to ensure that the displaypanel is secured within the base structure.

[0082] The electrode contacts (66 a) usually are thin film conductor orthick film conductor formed by sputtering, vacuum or vapor deposition,electroplating or lamination. The contact pads (66 b) of the basestructure used in the present invention may be in the form of anyelectrical connector, such as edge connector, elastomer connector,leaf-spring contacts, conductive adhesive, gold bumps or any other typeof connector that provides reliable contact.

[0083] While it is demonstrated in FIG. 6 that the right-hand side ofthe display panel is the side of insertion into the base structure, thedesign may be easily modified to have either one of the three othersides, top, bottom or left, to be the side of insertion on the displaypanel.

[0084] Furthermore, while it is demonstrated in FIG. 6 that the circuitdriver, controller and communication circuits on the circuit board arebuilt into the base structure, it is understood that the driver circuitmay be integrated into the display panel. Other components such as thecontroller and communication circuits may also be integrated into thedisplay panel. When the driver circuit is integrated into the displaypanel, the control signals and power are transmitted from the controllerto the driver through the electrode contacts (66 a) of the display paneland the contact pads (66 b) of the circuit board. In the case ofintegrating the driver, controller and communication circuits into thedisplay panel, only the power supply is provided through the contactpads. Depending on the application and system requirements, differentcircuitries may be integrated in the display panel to provide specificfunctions, such as wireless communication.

[0085]FIG. 7 illustrates an alternative design of the price tag system,which is similar to that of FIG. 6 except that there are multipleelectrode contacts (76 a) on the segment electrodes and each of theelectrode contacts (76 a) has a corresponding contact pad (76 b) on thecircuit board. This design allows an increase in number of the segmentelectrodes and also size of the segment electrodes. The reliability ofthe contact may also be improved.

[0086]FIG. 8 shows another alternative design of the present invention,which is also similar to that of FIG. 6, except that the display panel(80) is inserted into the base structure (81) from the front open faceof the structure. There is a hinged front plate (82), which, afterclosure, presses against the electrode contact area to ensure a reliablecontact between the electrode contacts (85 a) on the display panel andthe contact pads (85 b) on the circuit board. There is pressing foam(83) on the inside surface of the front plate for this purpose. Thefront plate also provides extra security to protect the display panel inthe base structure. As shown in FIG. 8, there may also be locking device(84 a and 84 b) to ensure complete closure of the front plate.

[0087] While it is demonstrated in FIG. 8 that the front plate is hingedat the right-hand side of the base structure, the design may be easilymodified to have the top plate hinged in either one of the three othersides, top, bottom or left, or non-hinged.

[0088] Similarly, while it is demonstrated in FIG. 8 that the circuitdriver, controller and communication circuits are built into the basestructure, it is understood that the driver circuit may be integratedinto the display panel. Other components on the circuit board may beintegrated into the display panel.

[0089]FIG. 9 shows a design similar to that of FIG. 8, except that ithas multiple electrode contacts (95 a) on the display panel andcorresponding contact pads (95 b) on the circuit board.

[0090] It is noted that the display panel of the price tag system mayhave the passive matrix electrode design of FIGS. 2A or 3A. The sameconnection system can be used for a passive matrix display panel.

[0091] The programming of the price tag system in any of the designsdemonstrated above can be accomplished through an I/O interface such asa serial port or through wireless communication, the latter beingpreferred.

[0092] The price tag system of the present invention has the advantagesof reliability, easy to install and low cost. It is much more costeffective than, for example, the ACF/FPC type connection. Using thesystem of the invention, the prices can be easily updated even from aremote location. In addition, if there is one defective panel, thedefective panel can be easily removed and replaced without any changesmade to the base structure. This also greatly reduces the operationcosts.

[0093] While the present invention has been described with reference tothe specific embodiments thereof, it should be understood that variouschanges may be made and equivalents may be substituted without departingfrom the true spirit and scope of the invention. In addition, manymodifications may be made to adapt to a particular situation. Forexample, while FIGS. 6-9 show only the typical numerical pattern forprice tag display, it is understood that the display pattern can beeasily modified for use in any types of electronic labeling systems. Allsuch modifications are intended to be within the scope of the claimsappended hereto.

What is claimed is:
 1. An electrophoretic display, comprising: a)display cells sandwiched between a top row electrode layer and a bottomcolumn electrode layer; b) row electrodes of said top row electrodelayer having substantially the same width and substantially the same gapin between; and c) column electrodes of said bottom column electrodelayer having substantially the same width and substantially the same gapin between.
 2. The display of claim 1 wherein said cells are preparedfrom the microcup technology.
 3. The display of claim 1 wherein said rowelectrodes and column electrodes are perpendicular to each other.
 4. Thedisplay of claim 1 wherein said row and column electrodes form anoblique angle from the direction of a support web.
 5. The display ofclaim 4 wherein said row electrodes have an angle of about 35° to about55° from the moving direction of a support web.
 6. The display of claim5 wherein said angle is about 45°.
 7. The display of claim 6 whereinsaid column electrodes have an angle of about 90° from the rowelectrodes.
 8. The display of claim 1 wherein the width of the rowelectrodes is the same as the width of the column electrodes.
 9. Thedisplay of claim 1 wherein the gap between the row electrodes is thesame as the gap between the column electrodes.
 10. A segment displaycomprising a common electrode layer and a segment electrode layer, whichcomprises a segment design in a repeated pattern.
 11. The display ofclaim 10 wherein said pattern is symmetrical in one or more directions.12. The display of claim 10 wherein said pattern is substantiallyseamless.
 13. The display of claim 10 wherein said common electrodelayer comprises electrodes having substantially the same width andsubstantially the same gap in between.
 14. The display of claim 13wherein said electrodes are perpendicular to the direction of a supportweb.
 15. The display of claim 10 wherein said electrode design issuitable for a digital clock display.
 16. The display of claim 10wherein said electrode design is suitable for a price tag display.
 17. Aelectrophoretic display system, which comprises: a) a base structure asa receptacle for an electrophoretic display panel; b) an electrophoreticdisplay panel insertable into the base structure and saidelectrophoretic display panel comprising display electrodes; and c) acircuit board comprising a driver circuit; said display electrodes arecapable of being in contact with said driver circuit to allow driving ofthe display panel by the driver circuit.
 18. The display system of claim17 wherein said display panel is a segment display panel having asegment design in a repeated pattern.
 19. The display system of claim 18wherein said segment display panel is for a digital clock display. 20.The display system of claim 18 wherein said segment display panel is fora price tag display.
 21. The display system of claim 17 wherein saiddisplay panel is a passive matrix display panel.
 22. The display systemof claim 17 wherein said contact is made through electrode contacts onelectrodes and contact pads in the base structure.
 23. The displaysystem of claim 22 wherein said electrode contacts are thin filmconductor or thick film conductor formed by sputtering, vacuum or vapordeposition, electroplating or lamination.
 24. The display system ofclaim 22 wherein said contact pads are in the form of an electricalconnector.
 25. The display system of claim 24 wherein said electricalconnector is an edge connector, elastomer connector, leaf-springcontacts, conductive adhesive or gold bumps.
 26. A price tag system,which comprises: a) a base structure as the receptacle for anelectrophoretic display panel; b) an electrophoretic display panelinsertable into the base structure wherein said electrophoretic displaypanel comprises segment electrodes having electrode contacts; c) acircuit board comprising a driver circuit and contact pads; said contactpads are capable of being in contact with said electrode contacts toallow driving of the display panel by the driver circuit.
 27. The systemof claim 26 wherein said driver circuit is programmed through an I/Ointerface or wireless communication.
 28. The system of claim 26 whereinsaid base structure further comprising a side-locking panel.
 29. Thesystem of claim 26 wherein said base structure further comprising afront plate.
 30. The system of claim 29 wherein said front plate has alocking device.
 31. The system of claim 26 wherein said electrodecontacts are thin film conductor or thick film conductor formed bysputtering, vacuum or vapor deposition, electroplating or lamination.32. The system of claim 26 wherein said contact pads are in the form ofan electrical connector.
 33. The system of claim 32 wherein saidelectrical connector is an edge connector, elastomer connector,leaf-spring contacts, conductive adhesive or gold bumps.
 34. The systemof claim 26 wherein each of said electrode contact has a correspondingcontact pad.
 35. The system of claim 26 wherein said circuit board ispart of the base structure.
 36. The system of claim 26 wherein saiddriver circuit is integrated into the display panel.
 37. The system ofclaim 26 wherein said circuit board further comprising controller andcommunication circuits.
 38. The system of claim 37 wherein said driver,controller and communication circuits are integrated into the displaypanel.
 39. The system of claim 26 wherein said electrophoretic displaypanel is formed of cells sandwiched between two electrode plates andfilled with an electrophoretic fluid.
 40. The system of claim 39 whereinsaid cells are further sealed with a sealing layer.
 41. The system ofclaim 40 wherein said sealing layer is a polymeric layer.
 42. The systemof claim 39 wherein said display panel is prepared from the microcuptechnology.